W7 - Epilepsy Flashcards
Briefly define “epilepsy”.
- The recurrent paroxysmal transient disturbance of brain function due to disturbance of electrical activity in the brain, where the disturbance is unrelated to infection or acute cerebral insult.
- A brain disorder characterized by an enduring predisposition to generate epileptic seizures and by the neurobiologic, cognitive, psychologic, and social consequences of this condition. A single seizure may qualify a patient for an epilepsy diagnosis if it is determined that the risk of additional seizures is “similar to the general recurrence risk (at least 60%) after 2 unprovoked seizures, occurring over the next 10 years.”
Characteristics: The disturbances may be manifested as episodic: - Loss of consciousness - Mental and behavioural disorders - Abnormal motor phenomena - Sensory disturbances - ANS perturbations Caused by abnormal hypersynchronous or hyperexcitable discharges of cortical neurons
Briefly define the following terms:
- Seizure
- Convulsion
- Fit
Seizure: The sudden attack or recurrence of a disease eg. Epileptic seizure
Convulsion: A violent involuntary contraction of voluntary muscles.
Fit: A sudden, acute attack or manifestation of a disease, especially one marked by convulsions or unconsciousness.
Briefly discuss the aetiology of:
- Primary epilepsy
- Secondary epilepsy
Primary epilepsy:
- Idiopathic - Inherited predisposition (precise genetic anomaly unknown)
- Some cases are undiagnosed secondary epilepsy
Secondary epilepsy:
- Occurs secondary to underlying conditions affecting CNS function; these conditions may be:
- Structural – CNS maldevelopment, brain tumour, arteriovenous malformation, traumatic brain injury.
- Metabolic – hypoglycemia, hypocalcemia, alcohol or substance withdrawal.
- Once underlying condition treated, seizures usually cease. However, if a permanent CNS lesion (eg scarring) has resulted seizures may continue.
List six (6) conditions which are known aetiological agents in secondary epilepsy.
Any six (6) of the following:
Structural lesions:
- CNS maldevelopment
- Brain tumour
- Post stroke defects
- Traumatic brain injury
- Infections (encephalitis, meningitis)
- Arteriovenous malformation
Metabolic lesions:
- Hypocalcaemia
- Hypoglycaemia
- Withdrawal (alcohol, sedatives)
Briefly discuss the classification of epilepsy.
Classification based primarily on onset, and consequent clinical manifestations.
I. Focal onset - Localised to a small part of the brain, but may spread to affect the entire brain.
II. Generalised onset - Affects the entire brain from the onset.
III. Unknown onset - No bystanders witnessed onset and thus can not be classified.
IV. Focal to bilateral (tonic-clonic) - Seizures start in one part of the brain and spread bilaterally as a tonic-clonic seizure.
V. Unclassified - Indicates that condition yet to be classified.
Indicate the frequency of each of the major types of epilepsy.
According to WHO, epilepsy is the world’s most common serious brain disorder
75% of epilepsy in young adults is primary epilepsy
Usually manifests between 2-14 years old
- Prevalence: 50/100,000 population
- Incidence: 50/100,000 per year
- Treatment: 70% of epileptics are successfully treated with established anti-epileptic drugs, over 50% of these patients will eventually be able to stop medication
Research suggests that 2-3% of the Australian population will develop epilepsy at some stage in their lives
Discuss the pathology of epilepsy.
In primary generalized epilepsy, MRI and CT may show foci of CNS:
- Atrophy
- Calcification
- Malformations.
In secondary epilepsy (especially focal), MRI and CT often show foci of CNS:
- Scarring
- Hamartomas (focal, non-neoplastic growth resulting from faulty development in an organ)
- Vascular malformations
- Tumours
PET good for identifying areas of CNS hypoperfusion and/or hypometabolism. Both of which may indicate the position of an epileptogenic region.
Note: Not all lesions discovered on CT, MRI and PET are associated with the development of epilepsy, many are just incidental findings.
List and describe the parts of the “typical” or generic epileptic seizure.
Seizure stages:
- Prodrome – Fatigue, irritability, poor sleep, changes to appetite
- Aura (focal, focal-to-bilateral) – flashing lights (occipital lobe aura), smells, motor stuff (eg lip smacking)
- Ictus – Epileptic fit. Type of seizure classified based on onset of ictus (eg tonic clonic, absence).
- Arousal – Transition from altered awareness to full awareness. Does not occur in focal seizures with full awareness, or absence seizures.
- Postictus – “Recovery time”, sufferer may feel fatigued. Does not occur in focal seizures.
Write notes on “partial seizures”
Partial seizures are now known as Focal seizures. They have clinical features that are referable to a region within one hemisphere.
Focal aware seizures:
- Awareness preserved
- EEG - Unilateral paroxysmal activity
- Clinical mainfestations - Depend on area of brain affected
Focal impaired awareness seizures:
- Awareness impaired
- EEG - Bilateral paroxysmal activity.
- Clinical manifestations:
- Behavioural arrest and staring (lasts 30-120s)
- Pt’s unaware and unresponsive
- May begin with aura (curious taste, smell etc)
- Automatisms (performing actions without conscious thought/intention) common. Consist of repetitive, stereotyped, purposeless, mild movements of hands (fidgeting, picking etc) and mouth (chewing, lip smacking etc)
- Other phenomena (confusion, wandering, fearfulness, incoherent speech) - often misconstrued as a psychological disorder
Focal to Bilateral Tonic-Clonic Seizures:
- Loss of awareness (often with convulsive motor activity)
In this case, clues to a focal origin to the seizure include:
- presence of an aura or observation of any focal feature (eg twitching eye, aphasia, tonic eye deviation)
- presence of post-ictal focal neurologic deficit.
Briefly discuss the pathophysiological theories pertaining to epilepsy.
A paroxysmal, excessive discharge of cerebral neurons results when a sudden imbalance occurs between the excitatory and inhibitory forces within a network of cortical neurons, in favour of a sudden onset net excitation.
It is not known why an epileptic discharge starts, spreads or stops. The pathophysiology of focal onset seizures differs from that of generalized-onset seizures → in both cases overall cellular excitability is increased, but the mechanisms of synchronization appear to substantially differ.
Some possible brain abnormalities that could result in epileptic seizures include:
- Intrinsic neuronal membrane dysfunction
- Abnormal neurotransmitter synthesis
- Abnormal neuronal enzymes
- Glial cell abnormalities
List four (4) factors which may induce a seizure in an epileptic.
- Hypoglycaemia
- Hypocalcemia
- Trauma
- Flashing lights
Write notes on absence seizures (Petit mal).
- Typically occurs in children.
- Onset - Sudden loss of awareness resulting in interruption of ongoing activities with potential brief upward deviation of eyes.
- Ssx of ictus - Fluttering eyelids (3 per sec), blank stare. Usually lasts 5-45s.
- Post-ictal period - Confusion. Pt usually unaware seizure has occurred (no arousal stage).
Children often classified as ‘daydreamers’, intelectually slow or even insolent as they may not respond when spoken to.
Write notes on events occurring during Generalised Onset Tonic-clonic seizures. In your answer you should list and briefly describe the characteristics of each of the stages of this seizure.
Tonic-clonic seizures are characterized by a tonic contraction phase, where the patient falls to the ground, and a clonic contraction phase, where they undergo jerking, rhythmic movements.
Stages:
I. Prodrome – May include a variety of Ssx (fatigue, irritability, appetite changes etc)
II. Loss of consciousness
III. Tonic contraction phase – Person completely still, appear paralysed with tonic contraction
IV. Clonic contraction phase – Rapid spasming, jerking movements
V. Flaccid relaxation – Muscles cease clonic contraction and become relaxed
VI. Arousal – Return of normal consciousness
VII. Postictal period – Can last mins-days. Person will feel fatigued due to energy expenditure during epileptic fit and may feel nauseous.
How is epilepsy diagnosed?
Made via the observation of clinical manifestations of the ictus (actual attack).
Most of the investigations are performed to exclude secondary causes of epilepsy.
The suggested investigations for a first seizure include:
- Clinical examination
- Assessment of seizure ssx – eyewitness account
- Routine lab tests – depending on clinical circumstances
- CSF – if encephalitis or subarachnoid haemorrhage is suspected.
- Drug screening
- Standard EEG (within 24 hours)
- Sleep deprived EEG (within 1 week)
- MRI
List the main therapeutic modalities which are used to treat epilepsy.
70% of epileptics are successfully treated with established anti-epileptic drugs – over 50% of these patients will eventually be able to stop medication.
Anti-convulsives (Dilantin) are normally used.
Marijuana has also been shown in some studies to be effective in reducing seizures.
